Tutorial RSS Feeds do not sort/display dates in readers

I've created a site that utilizes the RSS feed feature for ArticlePages that's described in the SS Tutorial.

The ArticleHolder works fine, of course, displaying ArticlePages in a list that's ordered by date.

Unfortunately, RSS readers (such as Google's RSS reader) do not recognize the dates in the list, nor do they sort the pages by date (I think they are sorting it by the drag/drop order within the SS CMS). How can I make the dates noticeable/sortable by RSS readers?